Great Andromeda Galaxy M31

The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda. It is also designated as M31 or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts.
Andromeda is the nearest spiral galaxy to the Milky Way, but not the closest galaxy overall. As it is visible from Earth as a faint smudge on a moonless night, it is one of the farthest objects visible to the naked eye, and can be seen even from urban areas with binoculars.
It gets its name from the area of the sky in which it appears, the Andromeda constellation, which was named after the mythological princess Andromeda. Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy, and about 30 other smaller galaxies.
Although the largest, Andromeda may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping. Based on recent research M31 contains one trillion stars, more than the number of stars in our own galaxy, which is estimated to be c. 200-400 billion.